On the occurrence of diphosphoinositol in the lipids of liver and pancreas

Abstract

• 1.

  1. The lipids of liver were reexamined for polyphosphoinositide, previously reported absent. The presence of a diphosphoinositide (DPI) was revealed by the isolation of inositol diphosphate (IP₂) from an acid hydrolysate, and its glyceryl derivative from an alkaline hydrolysate of the concentrated phospholipid fraction.

• 2.

  2. Starting with lipids extracted from liver and pancreas by azeotropic dehydration with 1,2-dichloroethane, materials soluble in acetone and alcohol were removed. After partition of the alcohol-insoluble phospholipids in CCl₄-light petroleum-methanol-H₂O (31:31:35:3, V/V), the non-polar fraction was assayed for inositol polyphosphate by chromatographic fractionation of the acid hydrolysate on Dowex-2 X8 Cl⁻ A diphosphate mixture eluted by NaCl or LiCl was separated by refractionation with a formate system yielding IP₂ and glycerol diphosphate.

• 3.

  3. The mixed glyceryl derivatives of IP₂ and glycerol diphosphate were secured by chromatographic fractionation of the alkaline hydrolysate. Based on the recovery of IP₂ and its glyceryl derivative, the content of DPI in the original pork liver lipid is 0.28 mmoles/kg.

• 4.

  4. DPI could not be extracted by ether from acetone-dehydrated fresh beef liver but was extracted with neutral chloroform-methanol (2:1, V/V).

• 5.

  5. Most of the IP₂ found in pacreatic lipid occured in material insoluble in CHCl₃ and in the CCl₄-light petroleum solvent.